Conventional flexible line vegetation trimmers, often called string trimmers, are well known to those in the art. See, for instance, U.S. Pat. Nos. 4,052,789, 4,054,992, 4,161,280, 4,209,902, 4,282,653 and 4,316,325. Each of these line trimmers discloses a rotating head from which protrudes at least one flexible cutting line. Most of the above-mentioned patents include a debris shield mounted over the cutting path of the flexible line to help protect the string trimmer operator from flying debris. Each of the aforesaid patents includes a knife blade depending from the debris shield or other structural member to cut the rotating flexible line or string to a predetermined length.
The problem arises with respect to the cut segments of flexible line or string. These segments are traveling at a relatively high speed, and a danger exists that the cut line segments may strike a human or animal in the vicinity of the operating string trimmer. If the human or animal is struck, serious damage could result.
U.S. Pat. No. 4,054,992 suggests, at column 6, lines 50-55 that the cutting lines should preferably be as light weight as possible so that when the line shears or breaks during use and pieces are thrown from the cutter head, such pieces will travel only a limited distance and will strike persons or other objects in the immediate vicinity with harmless impact if any. If the cutting line is of sufficient light weight so as to reduce the danger to persons or animals in the immediate vicinity, then the cutting line will have such reduced resistance to abrasion and the like upon operation as to be highly undesirable. Furthermore, smaller diameter lines have a higher probability of piercing skin upon impact, and for that reaon may be quite dangerous to those in close proximity to an operating string trimmer. In fact, a number of string trimmers are currently being offered on the commerical market in the United States with relatively heavy cutting lines, capable of relatively extended use before breaking due to abrasion or the like. It will be readily appreciated that these relatively heavy cutting lines, which are especially found in the heavy duty string trimmers, such as gasoline engine powered string trimmers, subject persons or animals in the immediate vicinity of the string trimmer to greater danger from being struck with cut line segments.